Electrowetting-on-dielectric characteristics of ZnO nanorods

Herein, we report the electrowetting-on-dielectric (EWOD) characteristics of ZnO nanorods (NRs) prepared via the hydrothermal method with different initial Zn²⁺ concentrations (0.03, 0.07, and 0.1 M). Diameter of the resultant ZnO NRs were 50, 70 and 85 nm, respectively. Contact angle (CA) measurements showed that the Teflon-coated ZnO NRs with diameters of 85 nm prepared from the 0.1 M solution had the highest CA (137°). During the EWOD studies, on the application of a voltage of 250 V, the water CA decreased to 78°, which demonstrates the potential application of this material in EWOD electronics. Furthermore, we explained the relationship between the applied voltage and CA based on the substrate nanostructures and our newly developed NR-on-film wetting model. In addition, we further validated our model by introducing the homo-composite dielectric structure, which is a composite of thin layered ZnO/Teflon and nano-roded ZnO/Teflon.